The present invention relates to the general field of transformers. In particular, the invention relates to a rotary three-phase transformer.
A rotary three-phase transformer serves to transfer energy and/or signals without contact between two axes rotating one relative to the other.
FIGS. 1 and 2 show respective rotary three-phase transformers 1 of the prior art.
The transformer 1 has three rotary single-phase transformers 2 corresponding to phases U, V, and W. Each rotary single-phase transformer 2 has a portion 3 and a portion 4 rotating one relative to the other about an axis A. By way of example, the portion 3 is a stator and the portion 4 is a rotor, or vice versa. In a variant, the portion 3 and the portion 4 are both movable in rotation relative to a stationary frame of reference (not shown). A toroidal coil 5 is received in a slot 6 defined by a body made of ferromagnetic material of the portion 3. A toroidal coil 7 is received in a slot 8 defined by a body made of ferromagnetic material of the portion 4. For each rotary single-phase transformer 2, the coils 5 and 7 form primary and secondary coils (or vice versa).
FIG. 1 shows a variant referred to as “U-shaped” in which the portion 3 surrounds the portion 4 about the axis A, while FIG. 2 shows a variant referred to as “E-shaped” or “pot-shaped”, in which the portion 3 and the portion 4 are one beside the other in the axial direction.
The three-phase transformer 1 of FIG. 1 or 2 presents weight and volume that are large since it is not possible to make best use of the magnetic fluxes of each of the phases, unlike a static three-phase transformer with forced fluxes in which it is possible to couple the fluxes. Furthermore, in the example of FIG. 2, it is necessary to use electrical conductors of sections that differ as a function of the distance between the axis of rotation and the phase, in order to conserve balanced resistances.
Document US 2011/0050377 describes a four-column rotary three-phase transformer. That transformer presents considerable weight and volume. That document also describes a five-column rotary three-phase transformer. That transformer presents considerable weight and volume. Furthermore, it makes use of radial winding passing via slots in the central columns of the magnetic circuit, where such winding is more complex to perform than the toroidal winding used in the transformers of FIGS. 1 and 2.
There thus exists a need to improve the topology of a three-phase transformer.